Truck doors of the type commonly referred to as roll-up or upwardly-acting types conventionally employ a plurality of door sections which are hinged together, with the door being rollingly supported on a pair of L-shaped tracks for permitting the door to move upwardly from a substantially vertical closed position into a substantially horizontal opened position. To permit this opening and closing movement, the door is provided with a plurality of roller-hinge units disposed adjacent the side edges of the door, which units not only hinge the adjacent door sections for permitting relative pivoting movement therebetween, but additionally support a roller which is rollingly engaged with and supported by the stationary L-shaped track. The roller-hinge unit conventionally employs a pair of hinge halves fixed to the adjacent door sections and disposed in opposed relationship, which hinge halves support a metal hinge tube in which a metal roller stem is axially floatably received so as to compensate for track variations. This roller stem in turn has a metal roller on the outer end thereof disposed for rolling engagement with the adjacent metal track. While large numbers of these roller-hinge units have operated satisfactorily for many years, nevertheless these known units have possessed features which have been less than optimum.
For example, the rolling of the roller on the track is undesirably noisy due to the metal-to-metal contact therebetween. Additional noise is also caused by the metal-to-metal contact between the hinge tube and the hinge halves pivotally supported thereon.
In an attempt to improve upon the known roller-hinge unit of the above-described type, particularly so as to minimize the noise, there has also been developed and utilized a roller-hinge unit employing a plastic roller provided with a rubber tire, with the roller being mounted on a metal roller stem which is press fit within the hinge tube. While this unit has been observed to reduce the noise, nevertheless this unit has possessed disadvantages. For example, in this unit the roller and stem are axially restrained relative to the hinge tube due to the press fit of the latter within the hinge halves. This makes it necessary to maintain precise tolerances with respect to the manufacture and assembly of the track, and particularly with respect to the mounting of the track relative to the door opening. Any misalignment or variation in the width between the tracks causes the roller to be sidewardly slidably displaced, causing rapid wear of the roller tread so as to result in the roller having a very short life expectancy.
A further problem associated with the known roller-hinge units is the looseness in the overall hinge connection, which looseness results from the large diametral clearance between the hinge tube and the hinge parts as stationarily mounted on the adjacent door sections. The known roller-hinge units have necessarily required substantial diametral clearance to permit the door to be manufactured with acceptable and achievable tolerance levels, and at the same time compensate for the substantial tolerances and variations which occur in the structure of the truck body and of the stationary tracks mounted thereon. These clearances have necessarily resulted in substantial looseness between adjacent door sections which further increase the noise generated by the unit during door operation, and additionally accelerates the wear of the cooperating parts.
It is thus an object of the present invention to provide an improved roller-hinge unit which substantially minimizes, if not eliminates, most of the above-mentioned disadvantages while at the same time permitting the door and the roller-hinge unit to be manufactured with practical and economical tolerances.
A further object is to provide an improved roller-hinge unit, as aforesaid, which utilizes a hinge tube constructed of a stiff plastic material, which hinge tube can be snapped into the cooperating hinge parts on the door section to provide a tighter hinged connection between the door sections, and at the same time provide a quiet slidable connection between the hinge tube and the roller stem which permits the latter to axially, and even rotatably, move relative to the hinge tube.
Still a further object is to provide a roller-hinge unit, as aforesaid, wherein the roller utilizes a tire tread constructed of polyurethane so as to greatly reduce the noise resulting from rolling engagement with the track, while at the same time providing the roller with maximum wear and durability.
It is also an object to provide a roller-hinge unit, as aforesaid, which can be manufactured and assembled efficiently and economically, which permits the door and the stationary track structure to possess maximum dimensional variations and tolerances while at the same time permitting proper compensation for these variations and tolerances, and which provides a highly durable and substantially quieter operation.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this type upon reading the following specification and inspecting the accompanying drawings.